Since the Canadiens were one of our earliest clients, it's possible you need to go under both Extensions and Themes, then remove the Canadiens elements from both locations (Menu bar, Tools --> Addons --> Extensions and then Themes). We fixed this a long time ago, but there could be something that didn't take during an update.

If that's not the issue, then one of our developers will have to get more details. Which will likely include which version of FF are you on, what operating system, and what other extensions are you running.